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Main  | Calendar  | Members  |	January 6, 2009

Considerations
• Larger diameter props provide more traction and breaking capabilities than smaller props pushing the same amount of air per revolution.
• Smaller diameter props will provide less air resistance when using a different diameter prop of the same pitch.
• For speed, select a smaller diameter prop that allows the engine to run in the maximum hp range for your engine.
• For vertical manuvers, or quick take-offs, select a larger diameter prop, that allows you engine to run in the maximum hp range.

For quick performance guesstimation, check your engines peak RPM against the props you are going to compare. Multiply the RPM by the calculate air volume in the following chart. The maximum Air Speed produced by your propeller will be RPM*Pitch/1056, or guesstimate in the field as (RPM(in thousands) * pitch). Examples are: 12000 * 6 / 1056 = 68.2 mph, and the same using quick field calcs is: 12 * 6 = 72 mph. The greater the propeller diameter the closer the model speed will be to the theoretical.

Graphical Information

Common Engine/Propeller Combinations
Engine	Rotational Volume	Prop Diameter
2 Stroke ABC
.049-.051	85-113	5.5X4-4.5	6X3-4
.09-.10	115-231	7X3-6
.15	151-352	7X5-6	8X3-7
.20-.25	302-393	8X6-7	9X4-6	10X5
.29-.35	314-509	9X6-8	10X4-6
.40		9.5X6	10X4-9	10.5X5-6	11X5-6
.45-.50		10X7-8	11X4-7.5
.60-.65		11X5-10	12X7-8	13X6-8
.71-.80		12X6-8	13X6-10	14X8
.90		13X6-10	14X6-8
1.08-1.20		14X8	15X8	16X6
1.5		16X8-10	18X6-8
1.8		18X8-10	20X6-8
2.1		20X8-10
4 Stroke
.20-.25		9X4-7
.30		9X5	10X6
.40		11X6	12X6
.50-.56		11X7-8	12X6-8
.60-65		11X8-9	12X6-8	13X6-8	14X5-6
.80-.91		11X9-11	12X8-10	13X6-9	14X6-8	15X4

Prop Diameter, Pitch, Single Rotation Volume Calculation
	Common Propeller Size
	Prop Diameter
Prop Pitch	5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2 39 57 77 101 127 157 190 226 265 308 353 402 454 509 567 628 3 59 85 115 151 191 236 285 339 398 462 530 603 681 763 851 942 4 79 113 154 201 254 314 380 452 531 616 707 804 908 1018 1134 1257 5 98 141 192 251 318 393 475 565 664 770 884 1005 1135 1272 1418 1571 6 118 170 231 302 382 471 570 679 796 924 1060 1206 1362 1527 1701 1885 7 137 198 269 352 445 550 665 792 929 1078 1237 1407 1589 1781 1985 2199 8 157 226 308 402 509 628 760 905 1062 1232 1414 1608 1816 2036 2268 2513 9 177 254 346 452 573 707 855 1018 1195 1385 1590 1810 2043 2290 2552 2827 10 196 283 385 503 636 785 950 1131 1327 1539 1767 2011 2270 2545 2835 3142 11 216 311 423 553 700 864 1045 1244 1460 1693 1944 2212 2497 2799 3119 3456 12 236 339 462 603 763 942 1140 1357 1593 1847 2121 2413 2724 3054 3402 3770 13 255 368 500 653 827 1021 1235 1470 1726 2001 2297 2614 2951 3308 3686 4084 14 275 396 539 704 891 1100 1330 1583 1858 2155 2474 2815 3178 3563 3969 4398 15 295 424 577 754 954 1178 1425 1696 1991 2309 2651 3016 3405 3817 4253 4712 16 314 452 616 804 1018 1257 1521 1810 2124 2463 2827 3217 3632 4072 4536 5027 17 334 481 654 855 1081 1335 1616 1923 2256 2617 3004 3418 3859 4326 4820 5341 18 353 509 693 905 1145 1414 1711 2036 2389 2771 3181 3619 4086 4580 5104 5655